A number of medical and cosmetic applications involve the controlled injection of substances into the body.
A medical syringe is a simple piston pump consisting of a plunger that fits tightly in a cylindrical barrel. The plunger can be pulled and pushed along inside the barrel, allowing the syringe to take in and expel a fluid through an orifice at the distal open end of the barrel. The distal end of the syringe is typically fitted with a hypodermic needle to transdermally introduce the fluid in the barrel into the body of a patient. Syringes are often used to administer injections. Surprisingly, other than the materials used to make them, the typical, conventional disposable syringes used for administering the advanced injectable substances or medicaments of today, are much the same as the very earliest syringe designs.
Unfortunately, the classic syringe/needle system is far from optimal for the administration of today's injectable aesthetic compositions. Hydrogel-based dermal fillers can be quite difficult to inject using the conventional syringe/needle system or conventional injection techniques. Many dermal fillers are by their nature highly viscous, thus requiring relatively high extrusion forces, especially when injected through preferred fine gauge needles. Moreover, these materials are typically injected into the face to correct wrinkles, including fine wrinkles as well as other minor defects in skin, and are therefore must be sometimes injected in trace amounts, and always with very high precision. Interestingly, these dermal fillers are commonly introduced into skin using quite standard needle and syringe combinations.
Using a traditional syringe, physicians are required to supply possibly significant force, which may reduce the practitioner's ability to control the syringe. Further, traditional syringes typically require the user's hand to be placed a significant distance from the site of the injection in order to operate the plunger, which may also lead to inaccuracy. Automated injection machines, which supply the force required to perform the injection using a motor, may reduce some of these problems. However, some motorized injection devices have the disadvantage that they may be heavy and bulky, requiring, for example, a battery which may add significantly to the weight of the device. This added bulk and weight may lead to a lack of control because of user fatigue, etc.
Systems have been developed and described for facilitating injection of dermal fillers. One such system is described in Mudd, U.S. patent application Ser. No. 12/994,568, filed Jan. 24, 2011, commonly owned herewith, the entire disclosure of which being incorporated herein by this reference. Mudd describes a handheld, motorized dermal filler injector that is capable of dispensing viscous injectable material at a low flow rate, for example, in some instances, a flow rate of only 0.001 ml/sec, at the high pressures necessary to extrude the fluid though a fine gauge needle.
The present invention provides an improved system for injecting dermal fillers, or other materials into skin, for example.